Communication Method, Apparatus, and System

ABSTRACT

A communication method, an apparatus, and a system in which a first session management function entity determines, based on information of a terminal group, user plane function entities accessed by terminals in a terminal group, and the first session management function entity determines a target user plane function entity based on the user plane function entities, where the target user plane function entity is used to perform communication between terminals in the terminal group. According to the method, the terminals in the terminal group are redirected to a same user plane function entity, namely, the target user plane function entity, so that communication between the terminals in the terminal group is locally implemented in the target user plane function entity. This shortens a communication path, and reduces a communication latency.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/824,267, filed on Mar. 19, 2020, which is a continuation ofInternational Application No. PCT/CN2018/107580, filed on Sep. 26, 2018,which claims priority to Chinese Patent Application No. 201710923300.0,filed on Sep. 30, 2017. All of the afore-mentioned patent applicationsare hereby incorporated by reference in their entireties.

TECHNICAL FIELD

Aspects of this application relate to the field of mobile communicationstechnologies, and in particular, to a communication method, anapparatus, and a system.

BACKGROUND

One of the development objectives of mobile communications is toestablish an extensive interconnection and interworking network thatincludes various types of terminals. This is also one of the startingpoints for developing the internet of things in a cellularcommunications framework currently. The internet of things enablesterminals in a terminal group that includes a plurality of terminals tocommunicate with each other.

Currently, the terminals usually communicate with each other by using a3rd generation partnership project (3GPP) network.

In some application scenarios, communication between the terminals inthe terminal group poses a relatively high requirement on a latency. Forexample, communication between vehicles in a platoon that includes aplurality of vehicles poses a very high requirement on a communicationlatency.

How to reduce a communication latency in a communication applicationscenario in which a relatively high requirement is imposed on a latencyis a problem which urgently needs to be resolved.

SUMMARY

Aspects of this application provides a communication method, anapparatus, and a system, so as to reduce a latency of communicationbetween terminals in a terminal group.

According to a first aspect, this application provides a communicationmethod. The method may be performed by a session management functionentity or a chip in the session management function entity. The sessionmanagement function entity may be an SMF entity in 5G communication, andmay be another entity having a session management function in futurecommunication. The communication method includes: A first sessionmanagement function entity determines, based on information of aterminal group, user plane function entities accessed by terminals in aterminal group. The first session management function entity determinesa target user plane function entity based on the user plane functionentities. The target user plane function entity is used to performcommunication between terminals in the terminal group. According to themethod, the terminals in the terminal group are redirected to a sameuser plane function entity, namely, the target user plane functionentity, so that communication between the terminals in the terminalgroup is locally implemented in the target user plane function entity.This shortens a communication path, and reduces a communication latency.

In a possible design, that the first session management function entitydetermines a target user plane function entity based on the user planefunction entities includes: The first session management function entityselects the target user plane function entity from the user planefunction entities accessed by the terminals or other user plane functionentities based on one or more of the following factors: a service rangeof each of the user plane function entities accessed by the terminals,locations of the terminals in the terminal group, a quantity ofterminals in the terminal group that are served by each of the userplane function entities accessed by the terminals, and a load of each ofthe user plane function entities accessed by the terminals. According tothe method, a plurality of factors are comprehensively considered, sothat a comparatively good user plane function entity can be selected asthe user plane function entity. This helps improve communicationquality.

In a possible design, the first session management function entity sendsa first notification message to the target user plane function entity.The first notification message includes tunnel information of a firstterminal, and a user plane function entity accessed by the firstterminal is different from the target user plane function entity. Themethod is used to update tunnel information of the target user planefunction entity, so as to implement local communication in the targetuser plane function entity.

In a possible design, the first session management function entity sendsa second notification message to a base station accessed by the firstterminal. The second notification message includes tunnel information ofthe target user plane function entity.

In a possible design, the first session management function entityreleases a resource of the user plane function entity accessed by thefirst terminal.

In a possible design, the first session management function entityreceives first instruction information from a policy control functionentity. The first instruction information is used to instruct the firstsession management function entity to select a user plane functionentity used by a terminal in the terminal group to performcommunication.

In a possible design, the first session management function entityreceives second instruction information from a policy control functionentity. The second instruction information is used to instruct the firstsession management function entity to select a user plane functionentity used by a second terminal in the terminal group to performcommunication, and the second terminal is a terminal that is in theterminal group and that corresponds to the first session managementfunction entity. That the first session management function entitydetermines a target user plane function entity based on the user planefunction entities includes: The first session management function entitydetermines the target user plane function entity based on a user planefunction entity accessed by the second terminal.

In a possible design, the first session management function entityreceives a first request message from a target network element. Thefirst request message is used to request the first session managementfunction entity to select a user plane function entity used by a thirdterminal in the terminal group to perform communication, and the thirdterminal is a terminal that is in the terminal group and thatcorresponds to the target network element. The first session managementfunction entity determines that the target user plane function entity isthe user plane function entity used by the third terminal to performcommunication. The target network element is a second session managementfunction entity or an access and mobility management function entity.According to the method, when the first request message is received fromthe target network element, the previously determined target user planefunction entity is used as a target user plane function entity of theterminal corresponding to the target network element, and there is noneed to reselect a target user plane function entity. This helps reduceoverheads.

In a possible design, the first request message includes tunnelinformation of a base station accessed by the third terminal, and tunnelinformation of a user plane function entity accessed by the thirdterminal.

In a possible design, the first session management function entityreceives a second request message from a target network element. Thesecond request message is used to request the first session managementfunction entity to select a user plane function entity used by a thirdterminal in the terminal group to perform communication, and the thirdterminal is a terminal that is in the terminal group and thatcorresponds to the target network element. That the first sessionmanagement function entity determines a target user plane functionentity based on the user plane function entities includes: The firstsession management function entity determines the target user planefunction entity based on a user plane function entity accessed by asecond terminal. The second terminal is a terminal that is in theterminal group and that corresponds to the first session managementfunction entity. The target network element is a second sessionmanagement function entity or an AMF entity.

In a possible design, the second request message includes tunnelinformation of a base station accessed by the third terminal, and tunnelinformation of a user plane function entity accessed by the thirdterminal.

In a possible design, the first session management function entityreceives the information of the terminal group from a control planefunction entity or an application server.

In a possible design, the information of the terminal group includes anidentifier of the terminal group and identifiers of the terminals in theterminal group. The first session management function entity stores thetarget user plane function entity and the identifier of the terminalgroup in contexts of the terminals in the terminal group. The contextsof the terminals in the terminal group are used by the first sessionmanagement function entity to obtain the target user plane functionentity from the contexts of the terminals in the terminal group.Alternatively, the first session management function entity locallystores a correspondence between the target user plane function entityand the identifier of the terminal group. The correspondence is used bythe first session management function entity to obtain the target userplane function entity from the correspondence. According to the method,the determined target user plane function entity is stored in thecontexts of the terminals or locally stored in the session managementfunction entity, so as to obtain the target user plane function entity.

According to a second aspect, this application provides a communicationmethod. The method may be performed by a policy control function entityor a chip in the policy control function entity. The policy controlfunction entity may be a PCF entity in 5G, and may be another entityhaving a policy control function in future communication. Thecommunication method includes: A policy control function entity obtainsinformation of a terminal group. The information of the terminal groupincludes at least identifiers of terminals in a terminal group. Thepolicy control function entity determines a first session managementfunction entity based on the identifiers of the terminals in theterminal group. The first session management function entity isconfigured to select a target user plane function entity, and the targetuser plane function entity is used to perform communication betweenterminals in the terminal group.

In a possible design, that the policy control function entity determinesa first session management function entity based on the identifiers ofthe terminals in the terminal group includes: The policy controlfunction entity determines, based on the identifiers of the terminals inthe terminal group, session management function entities accessed by theterminals in the terminal group. The policy control function entitydetermines the first session management function entity based on thesession management function entities accessed by the terminals.

In a possible design, that the policy control function entity determinesthe first session management function entity based on the sessionmanagement function entities accessed by the terminals includes: Thepolicy control function entity determines the first session managementfunction entity based on a quantity of terminals in the terminal groupthat are served by each of the session management function entitiescorresponding to the terminals in the terminal group.

In a possible design, that a policy control function entity obtainsinformation of a terminal group includes: The policy control functionentity receives the information of the terminal group from a controlplane function entity or an application server.

In a possible design, the policy control function entity sends firstinstruction information to the first session management function entity.The first instruction information is used to instruct the first sessionmanagement function entity to select a user plane function entity usedby a terminal in the terminal group to perform communication.

In a possible design, the policy control function entity sends secondinstruction information to the first session management function entity.The second instruction information is used to instruct the first sessionmanagement function entity to select a user plane function entity usedby a second terminal in the terminal group to perform communication, andthe second terminal is a terminal that is in the terminal group and thatcorresponds to the first session management function entity.

In a possible design, the policy control function entity sends anotification message to a target network element. The notificationmessage includes the information of the terminal group and addressinformation of the first session management function entity, and thenotification message is used to instruct the target network element toinsert the first session management function entity into a session of athird terminal in the terminal group, and instruct the first sessionmanagement function entity to select a user plane function entity usedby the third terminal to perform communication. The target networkelement is a second session management function entity or an AMF entity,and the third terminal is a terminal that is in the terminal group andthat corresponds to the target network element.

According to a third aspect, this application provides an apparatus. Theapparatus may be a session management function entity, or may be a chipin the session management function entity. The apparatus has functionsof implementing various designs of the first aspect. The functions maybe implemented by hardware, or may be implemented by hardware executingcorresponding software. The hardware or the software includes one ormore modules corresponding to the functions.

In a possible design, when the apparatus is the session managementfunction entity, the session management function entity includes aprocessing unit and a communications unit. The processing unit may be,for example, a processor. The communications unit may be, for example, atransceiver. The transceiver includes a radio frequency circuit.Optionally, the session management function entity further includes astorage unit. The storage unit may be, for example, a memory. When thesession management function entity includes a storage unit, the storageunit stores a computer executable instruction. The processing unit isconnected to the storage unit. The processing unit executes the computerexecutable instruction stored in the storage unit, so that the sessionmanagement function entity performs the communication method in thefirst aspect.

In another possible design, when the apparatus is the chip in thesession management function entity, the chip includes a processing unitand a communications unit. The processing unit may be, for example, aprocessor. The communications unit may be, for example, an input/outputinterface, a pin, or a circuit. The processing unit may execute acomputer executable instruction stored in a storage unit, so that thecommunication method in the first aspect is performed. Optionally, thestorage unit is a storage unit inside the chip, for example, a registeror a cache, or the storage unit may be a storage unit outside the chipin the session management function entity, for example, a read-onlymemory (ROM), another type of static storage device capable of storingstatic information and instructions, or a random access memory (RAM).

The processor mentioned above may be a general-purpose centralprocessing unit (CPU), a microprocessor, an application-specificintegrated circuit (ASIC), or one or more integrated circuits configuredto control program execution of the communication method in the firstaspect.

According to a fourth aspect, this application provides an apparatus.The apparatus may be a policy control function entity, or may be a chipin the policy control function entity. The apparatus has functions ofimplementing various designs of the second aspect. The functions may beimplemented by hardware, or may be implemented by hardware executingcorresponding software. The hardware or the software includes one ormore modules corresponding to the functions.

In a possible design, when the apparatus is the policy control functionentity, the policy control function entity includes a processing unitand a communications unit. The processing unit may be, for example, aprocessor. The communications unit may be, for example, a transceiver.The transceiver includes a radio frequency circuit. Optionally, thepolicy control function entity further includes a storage unit. Thestorage unit may be, for example, a memory. When the terminal includes astorage unit, the storage unit stores a computer executable instruction.The processing unit is connected to the storage unit. The processingunit executes the computer executable instruction stored in the storageunit, so that the policy control function entity performs thecommunication method in the second aspect.

In another possible design, when the apparatus is the chip in the policycontrol function entity, the chip includes a processing unit and acommunications unit. The processing unit may be, for example, aprocessor. The communications unit may be, for example, an input/outputinterface, a pin, or a circuit. The processing unit may execute acomputer executable instruction stored in a storage unit, so that thecommunication method in the second aspect is performed. Optionally, thestorage unit is a storage unit inside the chip, for example, a registeror a cache, or the storage unit may be a storage unit outside the chipin the policy control function entity, for example, a ROM, another typeof static storage device capable of storing static information andinstructions, or a RAM.

The processor mentioned above may be a general-purpose CPU, amicroprocessor, an ASIC, or one or more integrated circuits configuredto control program execution of the communication method in the secondaspect.

According to a fifth aspect, this application further provides acomputer-readable storage medium. The computer-readable storage mediumstores an instruction. When the instruction is run on a computer, thecomputer is enabled to perform the method in either of the foregoingaspects.

According to a sixth aspect, this application further provides acomputer program product including an instruction. When the instructionis run on a computer, the computer is enabled to perform the method ineither of the foregoing aspects.

In addition, for technical effects brought by any design manner of thesecond aspect to the sixth aspect, refer to technical effects brought bydifferent design manners of the first aspect. Details are not describedherein again.

These aspects or other aspects in this application are simpler andeasier to understand in descriptions in the following embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a schematic diagram of a communications system according toan embodiment of this application;

FIG. 1(b) is a schematic diagram of a possible network architectureaccording to an embodiment of this application;

FIG. 2 is a schematic diagram of a communication method according to anembodiment of this application;

FIG. 3 is a schematic diagram of a UPF and an SMF corresponding toterminals in a terminal group according to an embodiment of thisapplication;

FIG. 4 is another schematic diagram of a UPF and an SMF corresponding toterminals in a terminal group according to an embodiment of thisapplication;

FIG. 5 is another schematic diagram of a UPF and an SMF corresponding toterminals in a terminal group according to an embodiment of thisapplication;

FIG. 6 is a schematic diagram of a network architecture to whichEmbodiment 1 is applicable;

FIG. 7 is a schematic diagram of a communication method according to anembodiment of this application;

FIG. 8(a) is a schematic diagram of a network architecture to whichEmbodiment 2 is applicable;

FIG. 8(b) is another schematic diagram of a network architecture towhich Embodiment 2 is applicable;

FIG. 9 is a schematic diagram of a communication method according to anembodiment of this application;

FIG. 10(a) is a schematic diagram of a network architecture to whichEmbodiment 3 is applicable;

FIG. 10(b) is another schematic diagram of a network architecture towhich Embodiment 3 is applicable;

FIG. 11(a) is a schematic diagram of a network architecture to whichEmbodiment 4 is applicable;

FIG. 11(b) is another schematic diagram of a network architecture towhich Embodiment 4 is applicable;

FIG. 12 is a schematic diagram of a communication method according to anembodiment of this application;

FIG. 13 is a schematic diagram of an apparatus according to anembodiment of this application;

FIG. 14 is a schematic diagram of an apparatus according to anembodiment of this application; and

FIG. 15 is a schematic diagram of an apparatus according to anembodiment of this application.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

To make the objectives, technical solutions, and advantages of thisapplication clearer, the following further describes this application indetail with reference to the accompanying drawings. A specific operationmethod in a method embodiment may also be applied to an apparatusembodiment or a system embodiment. In the description of thisapplication, unless otherwise stated, “a plurality of” means two or morethan two.

FIG. 1(a) is a schematic diagram of a communications system according toan embodiment of this application. The communications system includes auser plane function entity and a session management function entity.Optionally, the communications system further includes either of anaccess and mobility management function entity and a policy controlfunction entity.

In the figure, there may be one or more user plane function entities,and there may be one or more session management function entities. Forease of description, an example in which there are one user planefunction entity and one session management function entity is used fordescription in the figure.

A target user plane function entity in user plane function entities isused to perform communication between terminals in a terminal group.

The session management function entity is configured to: determine,based on information of a terminal group, user plane function entitiesaccessed by terminals in the terminal group, and determine the targetuser plane function entity based on the user plane function entities.

In an implementation, the session management function entity furtherselects the target user plane function entity from the user planefunction entities accessed by the terminals or other user plane functionentities based on one or more of the following factors: a service rangeof each of the user plane function entities accessed by the terminals,locations of the terminals in the terminal group, a quantity ofterminals in the terminal group that are served by each of the userplane function entities accessed by the terminals, and a load of each ofthe user plane function entities accessed by the terminals.

In an implementation, the session management function entity furthersends a first notification message to the target user plane functionentity. The first notification message includes tunnel information of afirst terminal, and a user plane function entity accessed by the firstterminal is different from the target user plane function entity.

In an implementation, the session management function entity sends asecond notification message to a base station accessed by the firstterminal. The second notification message includes tunnel information ofthe target user plane function entity.

The policy control function entity is configured to: obtain informationof a terminal group, where the information of the terminal groupincludes at least identifiers of terminals in the terminal group; anddetermine a first session management function entity based on theidentifiers of the terminals in the terminal group, where the firstsession management function entity is configured to select a target userplane function entity, and the target user plane function entity is usedto perform communication between terminals in the terminal group.

In an implementation, the policy control function entity determines,based on the identifiers of the terminals in the terminal group, sessionmanagement function entities accessed by the terminals in the terminalgroup, and determines the first session management function entity basedon the session management function entities accessed by the terminals.

In an implementation, the policy control function entity may determinethe first session management function entity based on a quantity ofterminals in the terminal group that are served by each of the sessionmanagement function entities corresponding to the terminals in theterminal group.

In an implementation, the policy control function entity sends secondinstruction information to the first session management function entity.The second instruction information is used to instruct the first sessionmanagement function entity to select a user plane function entity usedby a second terminal in the terminal group to perform communication, andthe second terminal is a terminal that is in the terminal group and thatcorresponds to the first session management function entity.

In an implementation, the policy control function entity sends anotification message to a target network element. The notificationmessage includes the information of the terminal group and addressinformation of the first session management function entity, and thenotification message is used to instruct the target network element toinsert the first session management function entity into a session of athird terminal in the terminal group, and instruct the first sessionmanagement function entity to select a user plane function entity usedby the third terminal to perform communication. The target networkelement is a second session management function entity or an access andmobility management function entity, and the third terminal is aterminal that is in the terminal group and that corresponds to thetarget network element. Optionally, any two, any three, or all of theuser plane function entity, the session management function entity, theaccess and mobility management function entity, and the policy controlfunction entity in FIG. 1(a) may be implemented by one entity device, ormay be jointly implemented by a plurality of entity devices, or may beone logical function module in one entity device. This is notspecifically limited in this embodiment of this application.

It should be noted that a communication method according to anembodiment of this application may be performed by an apparatus. Theapparatus may be a session management function entity or a chip in thesession management function entity, or may be a policy control functionentity or a chip in the policy control function entity.

In a fifth-generation (5G) mobile communications technology, the sessionmanagement function entity is also referred to as an SMF (sessionmanagement function) entity, the user plane function entity is alsoreferred to as a UPF (user plane function), the policy control functionentity is also referred to as a PCF (policy control function) entity,and the access and mobility management function entity is also referredto as an AMF (Access and Mobility Management Function) entity. In futurecommunication, the session management function entity, the policycontrol function entity, and the access and mobility management functionentity may have other names.

For ease of description, in this application, the communication methodis described by using an example in which the apparatus is the sessionmanagement function entity or the policy control function entity. For animplementation method when the apparatus is the chip in the sessionmanagement function entity or the chip in the policy control functionentity, refer to specific descriptions of the communication methodperformed by the session management function entity or the policycontrol function entity. No repeated description is provided.

In this application, a method of communication between terminals in aterminal group is described. Terminals in one terminal group may berepresented by terminal identifiers of the terminals, and the terminalgroup includes at least two terminals. In specific application, eachterminal in the terminal group may be, for example, a communicationsapparatus in one vehicle in a platoon. In other words, each vehicle inthe platoon has one communications apparatus. A set of communicationsapparatuses in all vehicles forms one terminal group. Communicationbetween terminals in the terminal group may be used to indicatecommunication between vehicles in the platoon.

Certainly, in another application scenario, the terminals in theterminal group may further have other meanings. For example, a setincluding a plurality of control units in a factory may also be referredto as one terminal group. A specific application scenario of theterminals in the terminal group is not limited in this application.

FIG. 1(b) is a schematic diagram of a possible network architectureaccording to an embodiment of this application. The network architectureis a 5G network architecture. Network elements in the 5G architectureinclude an AMF entity, an SMF entity, and a user plane function UPFentity, and may further include a PCF entity, a terminal (an example inwhich the terminal is user equipment (UE) and is used in the figure), aradio access network (Radio Access Network, RAN), a unified datamanagement (UDM) entity, and the like. In an application domain, thenetwork elements in the 5G architecture include a control plane functionentity and an application server. The control plane function entity ismainly responsible for terminal authentication, application servermanagement, interaction with a control plane on a network side, and thelike. The application server is mainly responsible for providing serviceauthentication and a specific service for a terminal. For example, invehicle-to-everything communication, the control plane function entitymay be a vehicle-to-everything communication control function (V2XControl Function) entity, and the application server may be avehicle-to-everything communication application server (V2X ApplicationServer), and may be configured to perform remote driving, trafficinformation distribution, and the like.

The RAN device communicates with the AMF entity through an N2 interface.The RAN device communicates with the UPF entity through an N3 interface.The UPF entity communicates with the SMF entity through an N4 interface.The PCF entity communicates with the control plane control entitythrough an N5 interface. The SMF entity communicates with the PCF entitythrough an N7 interface. The AMF entity communicates with the UDM entitythrough an N8 interface. The UPF entity communicates with the UPF entitythrough an N9 interface. The SMF entity communicates with the UDM entitythrough an Mo interface. The AMF entity communicates with the SMF entitythrough an Nil interface. The AMF entity communicates with the PCFentity through an N15 interface.

A main function of the RAN is to control a user to access a mobilecommunications network wirelessly. The RAN is a part of a mobilecommunications system, and implements a radio access technology.Conceptually, the RAN resides on a device (such as a mobile phone, acomputer, or any remote control machine), and provides a connection to acore network. The RAN device includes but is not limited to: a gNodeB(gNB) in 5G, an evolved NodeB (eNB), a radio network controller (RNC), aNodeB (NB), a base station controller (BSC), a base transceiver station(BTS), a home base station (for example, a home evolved nodeB or a homenode B, HNB), a baseband unit (BBU), a transmission reception point(TRP), a transmission point (TP), a mobile switching center, and thelike. In addition, the RAN device may further include a wirelessfidelity (Wi-Fi) access point (AP) and the like.

The AMF entity is responsible for access management and mobilitymanagement of the terminal. In actual application, the AMF entityincludes a mobility management function in a mobility management entity(MME) in a network framework in long term evolution (LTE), and furtherhas an access management function.

The SMF entity is responsible for session management, for example,session establishment of the user.

The UPF entity is a user plane function network element, and is mainlyresponsible for accessing an external network. The UPF entity includesrelated functions of a serving gateway (SGW) and a public data networkgateway (PDN-GW) in LTE.

The UDM entity may store subscription information of the user, andimplement a backend similar to a home subscriber server (HSS) in 4G.

The PCF entity is configured to perform policy control, and is similarto a policy and charging rules function (PCRF) unit in 4G. The PCFentity is mainly responsible for generating policy authorization,quality of service (QoS), and a charging rule, and delivering acorresponding rule to the UPF entity by using the SMF entity, tocomplete installation of the corresponding policy and rule.

The terminal in this application is a device having wireless receivingand sending functions, and may be deployed on land, for example, anindoor or outdoor device, a handheld device, or a vehicle-mounteddevice, or may be deployed on water (for example, on a steamship), ormay be deployed in the air (for example, on an airplane, a balloon, or asatellite). The terminal may be a mobile phone, a tablet computer (pad),a computer having wireless receiving and sending functions, a virtualreality (VR) terminal, an augmented reality (AR) terminal, a wirelessterminal in industrial control, a wireless terminal in self driving, awireless terminal in remote medical, a wireless terminal in smart grid,a wireless terminal in transportation safety, a wireless terminal insmart city, a wireless terminal in smart home, or the like. For example,UE in FIG. 1(b) is a specific example of the terminal.

It should be noted that a RAN device, an SMF entity, a UPF entity, anAMF entity, a PCF entity, a UDM entity, and the like in FIG. 1(b) aremerely names, and the names constitute no limitation on the devices. Ina 5G network and another future network, network elements or entitiescorresponding to the RAN device, the SMF entity, the UPF entity, the AMFentity, the PCF entity, and the UDM entity may have other names. This isnot specifically limited in this embodiment of this application.

For ease of description, in this application, a system architectureshown in FIG. 1(b) is used as a specific embodiment to describe thesolutions of this application.

For the system architecture shown in FIG. 1(b), one SMF entity maymanage a plurality of UPF entities, and a set of service ranges of theplurality of UPF entities is a service range of the SMF entity. That theSMF entity manages the plurality of UPF entities may also be referred toas that the SMF entity corresponds to the plurality of UPF entities.

For terminals in a terminal group, after sessions such as a packet dataunit (PDU) sessions of the terminals are established, each of user planepaths of the terminals includes one or more UPF entities. In this case,these UPF entities may be accessed by the terminals, or may be referredto as UPF entities corresponding to the terminals, or may be referred toas UPF entities on session paths of the terminals, or may be referred toas UPF entities serving the terminals, which all represent a samemeaning. Different representation manners are alternately usedsubsequently in this application.

After the sessions of the terminals are established, each of controlplane paths of the terminals includes one or more SMF entities. TheseSMF entities may be referred to as SMF entities configured to manage theterminals, or may be referred to as SMF entities on the control planepaths of the sessions of the terminals, or may be referred to as SMFentities corresponding to the terminals, or may be referred to as SMFentities serving the terminals, which all represent a same meaning.Different representation manners are alternately used subsequently inthis application.

Currently, according to a prior-art solution, when terminals in aterminal group communicate with each other, communication data needs topass through all UPF entities on user plane paths of terminals.

For example, for UE 1 and UE 2 in the terminal group, if UPF entitiesincluded on a user plane path of a terminal 1 are a UPF 1 and a UPF 2, aRAN 1 is a base station accessed by the UE 1, and the UPF 1 is a UPFconnected to the RAN 1. If UPF entities included on a user plane path ofthe UE 2 are a UPF 3 and a UPF 4, the RAN 1 is a base station accessedby the UE 2, and the UPF 3 is a UPF connected to a RAN 2.

According to a prior-art communication method, a path through whichcommunication data between a terminal 1 and a terminal 2 passes is asfollows:

Terminal 1->RAN 1->UPF 1->UPF 2->data network (DN)->UPF 4->UPF 3->RAN2->terminal 2.

It can be learned that, when there are a plurality of UPF entities on auser plane path of the terminal 1, or there are a plurality of UPFentities on a user plane path of the terminal 2, communication betweenthe terminal 1 and the terminal 2 needs to pass through each UPF entityon the user plane path. Consequently, a path of the communication datais prolonged, and a relatively great latency between terminals iscaused.

To resolve the foregoing and/or other problems, this applicationprovides a communication method which is applicable to the systemarchitectures shown in FIG. 1(a) and FIG. 1(b). The communication methodcan reduce a latency of communication between terminals in a terminalgroup.

For ease of description, an example in which the session managementfunction entity is an SMF entity, the policy control function entity isa PCF entity, and the user plane function entity is a UPF entity is usedfor description in this application.

The following specifically describes the communication method in thisapplication. FIG. 2 shows a communication method according to anembodiment of this application. The communication method includes thefollowing steps.

Step 201: A first SMF entity determines, based on information of aterminal group, UPF entities accessed by terminals in a terminal group.

The first SMF entity is an SMF entity configured to select a target UPFentity. For example, when SMF entities corresponding to the terminals inthe terminal group are a same SMF entity, the SMF entity is the firstSMF entity.

For another example, when SMF entities corresponding to the terminals inthe terminal group are a plurality of SMF entities, a PCF entity selectsone SMF entity from the plurality of SMF entities to serve as the firstSMF entity.

For another example, an SMF entity other than SMF entities correspondingto the terminal group may be selected as the first SMF entity. In otherwords, the selected first SMF entity is not in the SMF entitiescorresponding to the terminals in the terminal group.

The information of the terminal group includes at least identifiers ofthe terminals in the terminal group, and optionally, further includes anidentifier of the terminal group. The information of the terminal groupmay be from the PCF entity, or may be from another SMF entity, or may befrom an AMF entity. Descriptions are separately provided subsequentlybased on different cases.

The first SMF entity may obtain at least session contexts such as PDUsession contexts of the terminals in the terminal group based on theinformation of the terminal group. A UPF entity accessed by a terminalserved by the first SMF entity may be obtained based on the sessioncontexts of the terminals.

For example, the terminal group includes UE 1, UE 2, and UE 3. The UE 1corresponds to a UPF 1, the UE 2 corresponds to a UPF 2, and the UE 3corresponds to a UPF 3. The UPF 1 and the UPF 2 are UPF entities coveredby the first SMF entity, and the UPF 3 is a UPF entity that is notcovered by the first SMF entity. In this case, the first SMF entityobtains the UPF 1 and the UPF 2 based on the contexts of the terminals,in other words, determines that the UPF entities accessed by theterminals in the terminal group are {UPF 1, UPF 2}.

Step 202: The first SMF entity determines a target UPF entity based onthe UPF entities.

The target UPF entity is configured to perform communication betweenterminals in the terminal group. The communication herein is localcommunication, and may also be understood as closed-loop communication.To be specific, after receiving communication data from a firstterminal, the target UPF entity sends, by using local routinginformation, the communication data to a base station accessed by asecond terminal or to a UPF entity accessed by the second terminal,instead of sending the communication data to another UPF entity accessedby the first terminal or to a DN (definition network) like in the priorart.

For example, for UE 1 and UE 2 in the terminal group, if UPF entitiesincluded on a user plane path of a terminal 1 are a UPF 1 and a UPF 2, aRAN 1 is a base station accessed by the UE 1, and the UPF 1 is a UPFconnected to the RAN 1. If UPF entities included on a user plane path ofthe UE 2 are a UPF 3 and a UPF 4, the RAN 1 is a base station accessedby the UE 2, and the UPF 3 is a UPF connected to a RAN 2.

According to a prior-art communication method, a path through whichcommunication data between a terminal 1 and a terminal 2 passes is asfollows:

UE 1->RAN 1->UPF 1->UPF 2->DN->UPF 4->UPF 3->RAN 2->UE 2.

However, according to the communication method in this application, ifthe UPF 1 is selected as the target UPF entity, a path through whichcommunication data between the UE 1 and the UE 2 passes may be asfollows:

UE 1->RAN 1->UPF 1 (target UPF)->RAN 2->UE 2.

Alternatively, a path through which communication data between the UE 1and the UE 2 passes may be as follows:

UE 1->RAN 1->UPF 1 (target UPF)->UPF 3->RAN 2->UE 2.

Alternatively, a path through which communication data between the UE 1and the UE 2 passes may be as follows:

UE 1->RAN 1->UPF 1 (target UPF)->UPF 4->UPF 3->RAN 2->UE 2.

A specific manner to be used may be determined based on an actualrequirement. Preferably, the first implementation method may be used, inother words, UE 1->RAN 1->UPF 1 (target UPF)->RAN 2->UE 2.

It should be noted that the RAN 1 and the RAN 2 may be a same RAN, ormay be different RANs. This is not limited.

In the foregoing several updated paths provided in this application,regardless of a specific path to be used, compared with the prior art, aforwarding path of communication data between terminals is shortened.Particularly, for the foregoing first implementation method, theterminals in the terminal group are redirected to a same UPF entity,namely, the target UPF entity, so that communication between terminalsin the terminal group is locally implemented in the target UPF entity.This shortens a communication path, and reduces a communication latency.

The following provides descriptions with reference to specific examplesbased on different cases.

Case 1: The terminals in the terminal group access a same UPF entity,and correspond to a same SMF entity.

In the case 1, when all the terminals in the terminal group correspondto a same SMF entity, in other words, are managed by a same SMF entity,the PCF entity determines that the SMF entity is the first SMF entity.The PCF entity sends first instruction information to the first SMFentity. The first instruction information is used to instruct the firstSMF entity to select a UPF entity used by a terminal in the terminalgroup to perform communication. The instruction information carries theinformation of the terminal group. The information of the terminal groupincludes identifiers of the terminals in the terminal group, andoptionally, further includes an identifier of the terminal group.

When all the terminals in the terminal group access a same UPF entity,the first SMF entity determines that the UPF entity is the target UPFentity.

FIG. 3 is a schematic diagram of a UPF and an SMF corresponding toterminals in a terminal group according to an embodiment of thisapplication. The terminal group includes five terminals, which arerespectively UE 1, UE 2, UE 3, UE 4, and UE 5. In addition, the fiveterminals access a same UPF entity on a user plane path, and are managedby a same SMF entity on a control plane path.

In this example, the PCF entity determines that the SMF entity is thefirst SMF entity, and the first SMF entity determines that the UPFentity is the target UPF entity.

Further, in an implementation, the first SMF entity further createslocal routing information, and sends the local routing information tothe target UPF entity. The local routing information is used to recordan association relationship between a downlink tunnel of each terminalin the terminal group and the terminal, so that the target UPF entitycan forward communication data of a source terminal to a destinationterminal based on the local routing information. The communication dataincludes address information of the destination terminal.

Certainly, in another implementation, if the target UPF entity has alocal routing capability, the first SMF entity does not need to sendlocal routing information to the target UPF entity, but only needs tosend instruction information to the target UPF entity, to instruct thetarget UPF entity to perform local routing. In this way, communicationdata of a source terminal can also be directly forwarded to adestination terminal.

In another implementation, if the target UPF entity has a local routingcapability, the first SMF entity may send neither local routinginformation nor instruction information to the target UPF entity. Inother words, the target UPF entity has a local communication capability.

In any one of the foregoing implementations, optionally, the first SMFentity may send information such as some charging rules to the targetUPF entity.

Case 2: The terminals in the terminal group access different UPFentities, and correspond to a same SMF entity.

In the case 2, when all the terminals in the terminal group correspondto a same SMF entity, in other words, are managed by a same SMF entity,the PCF entity determines that the SMF entity is the first SMF entity.

After determining the first SMF entity, the PCF entity sends firstinstruction information to the first SMF entity. The first instructioninformation is used to instruct the first SMF entity to select a UPFentity used by a terminal in the terminal group to performcommunication. In other words, the PCF entity instructs, by using thefirst instruction information, the first SMF entity to select the targetUPF entity.

In the case 2, because the terminals in the terminal group accessdifferent UPF entities, the first SMF entity needs to select one UPFentity from these UPF entities to serve as the target UPF entity.Certainly, the first SMF entity may select the target UPF entity fromother UPF entities.

The first SMF entity may select the target UPF entity from UPF entitiesaccessed by the terminals in the terminal group or other UPF entitiesbased on one or more of the following factors: a factor 1, a factor 2,and a factor 3.

The factor 1 is a service range of each of the UPF entities accessed bythe terminals and locations of the terminals in the terminal group.

The factor 2 is a quantity of terminals in the terminal group that areserved by each of the UPF entities accessed by the terminals.

The factor 3 is a load of each of the UPF entities accessed by theterminals.

FIG. 4 is a schematic diagram of a UPF and an SMF corresponding toterminals in a terminal group according to an embodiment of thisapplication. The terminal group includes five terminals, which arerespectively UE 1, UE 2, UE 3, UE 4, and UE 5. In addition, the UE 1 tothe UE 3 access a UPF 1, the UE 4 accesses a UPF 2, and the UE 5accesses a UPF 3 on a user plane path, and the UE 1 to the UE 5 are allmanaged by a same SMF entity on a control plane path.

With reference to the example shown in FIG. 4 , for the factor 1, thetarget UPF entity may be selected based on the relation between aservice range of each of the UPF 1 to the UPF 3 and a location of eachof the UE 1 to the UE 5, for example, whether the UE is comparativelyclose to a central location of the service range of the UPF entity. Ashorter distance indicates a lower probability that the UPF entity ismoved out. Generally, if a distance between every two of the terminalsin the terminal group is relatively short, the terminals in the terminalgroup may be used as a whole physically, and a UPF entity is selectedbased on a physical location relationship between the terminal group andthe UPF entity. Specifically, if the terminal group is closer to acentral location of the UPF entity, it is more likely to select the UPFentity.

With reference to the example shown in FIG. 4 , for the factor 2, thetarget UPF may be selected based on the quantity of terminals in theterminal group that are served by each UPF entity. For example, a UPFentity that serves a largest quantity of terminals is selected as thetarget UPF entity. For FIG. 4 , if the UPF 1 serves three terminals, theUPF 2 serves one terminal, and the UPF 3 serves one terminal, the UPF 1is preferentially selected as the target UPF entity.

With reference to the example shown in FIG. 4 , for the factor 3, thetarget UPF may be selected based on the load of each of the UPF entitiesaccessed by the terminals. For example, a UPF entity having a lowestload is selected as the target UPF entity.

The target UPF entity may be specifically selected based on one or moreof the foregoing factors. The target UPF may be a UPF entity in the UPFentities accessed by the terminals in the terminal group, or may be aUPF entity other than the UPF entities accessed by the terminals in theterminal group. The UPF entity is also managed by the first SMF entity.For example, another UPF entity may be selected when a comparativelygood UPF entity cannot be selected from the UPF entities accessed by theterminals in the terminal group, based on the foregoing factors.

For the example shown in FIG. 4 , the UPF 1 is finally selected as thetarget UPF entity. In this case, when every two of the UE 1 to the UE 5need to communicate with each other, local forwarding may be performedby using the UPF 1. For example, if the UE 1 sends communication data tothe UE 4, a communication path of the communication data may be: UE1->RAN 1->UPF 1->RAN 2->UE 4. In the prior art, the communication pathof the communication data is: UE 1->RAN 1->UPF 1->DN->UPF 2->RAN 2->UE4. Apparently, the method in this application can shorten a transmissionpath of communication data, and can reduce a latency.

Case 3: The terminals in the terminal group access different UPFentities, and correspond to different SMF entities.

In the case 3, when the terminals in the terminal group correspond todifferent UPF entities, the PCF entity may select one SMF entity fromthese SMF entities to serve as the first SMF entity.

For example, the PCF entity may obtain the information of the terminalgroup. The information of the terminal group includes at least theidentifiers of the terminals in the terminal group, and optionally,further includes the identifier of the terminal group. The identifier ofthe terminal group is used to identify the terminal group, and theidentifiers of the terminals are used to identify the terminals.

Specifically, the PCF entity may receive the information of the terminalgroup from a control plane function entity or an application server. Theinformation of the terminal group in the control plane function entityor the application server may be generated when the control planefunction entity or the application server establishes the terminalgroup, or may be sent to the control plane function entity or theapplication server after a specific terminal in the terminal groupestablishes the terminal group.

After obtaining the information of the terminal group, the PCF entitymay determine the first SMF entity based on the identifiers of theterminals in the terminal group. For example, the PCF entity determines,based on the identifiers of the terminals in the terminal group by usingcontexts corresponding to the terminal identifiers, an SMF entitycorresponding to each terminal. For example, FIG. 5 is a schematicdiagram of a UPF and an SMF corresponding to terminals in a terminalgroup according to an embodiment of this application. The terminal groupincludes five terminals, which are respectively UE 1, UE 2, UE 3, UE 4,and UE 5. In addition, the UE 1 to the UE 3 access a UPF 1, the UE 4accesses a UPF 2, and the UE 5 accesses a UPF 3 on a user plane path,and the UE 1 to the UE 4 correspond to an SMF 1, and the UE 5corresponds to an SMF 2 on a control plane path. Therefore, it may bedetermined that SMF entities corresponding to the terminals in theterminal group are the SMF 1 and the SMF 2.

Then, an SMF entity is selected from the SMF 1 and the SMF 2 to serve asthe first SMF entity. Before the first SMF entity is selected, in animplementation, the PCF entity determines the first SMF entity based ona quantity of terminals in the terminal group that are served by each ofSMF entities corresponding to the terminals in the terminal group. Forexample, for FIG. 5 , if terminals served by the SMF 1 are the UE 1 tothe UE 4, namely, four terminals, and terminals served by the SMF 2 arethe UE 5, namely, one terminal, the SMF 1 is selected as the first SMF.Certainly, in specific application, the first SMF entity may be selectedaccording to another method. For example, an SMF entity other than theSMF entities corresponding to the terminal group may be selected as thefirst SMF entity. In other words, the selected first SMF entity is notin the SMF entities corresponding to the terminals in the terminalgroup. This is not specifically limited in this application.

After determining the first SMF entity, the PCF entity may determine,based on information about the terminals in the terminal group, a methodfor instructing the first SMF entity to select a UPF entity configuredto perform communication between terminals in the terminal group. Forexample, there are at least the following two instruction methods.

Instruction method 1: The PCF entity sends second instructioninformation to the first SMF entity, and then sends a notificationmessage to a target network element.

The target network element is an AMF entity or a second SMF entity.

The second SMF entity is an SMF entity in the SMF entities correspondingto the terminals in the terminal group other than the first SMF entity.For example, referring to FIG. 5 , if the SMF 1 is the first SMF entity,the SMF 2 is the second SMF entity.

Specifically, the PCF entity first sends the second instructioninformation to the first SMF entity. The second instruction informationis used to instruct the first SMF entity to select a UPF entity used bya second terminal in the terminal group to perform communication. Thesecond terminal is a terminal that is in the terminal group and that ismanaged by the first SMF entity, or the second terminal may beunderstood as a terminal that is in the terminal group and thatcorresponds to the first SMF entity. With reference to FIG. 5 , thesecond terminal is any one of the UE 1 to the UE 4.

Because the first SMF entity manages some terminals, the first SMFentity may select a target UPF entity for the terminals managed by thefirst SMF entity. For example, the first SMF entity selects the UPF 1 asthe target UPF entity.

After selecting the target UPF entity, the first SMF entity stores thetarget UPF entity. A storage method includes but is not limited to thefollowing methods.

Storage method 1: The target UPF entity and the identifier of theterminal group are stored in the session contexts of the terminals inthe terminal group.

For example, the target UPF entity is the UPF 1, and the sessioncontexts of the terminals are as follows:

A session context of the UE 1 includes the identifier of the terminalgroup and an identifier of the UPF 1.

A session context of the UE 2 includes the identifier of the terminalgroup and the identifier of the UPF 1.

A session context of the UE 3 includes the identifier of the terminalgroup and the identifier of the UPF 1.

A session context of the UE 4 includes the identifier of the terminalgroup and the identifier of the UPF 1.

A session context of the UE 5 includes the identifier of the terminalgroup and the identifier of the UPF 1.

For another example, the session contexts of the terminals may be asfollows:

A session context of the UE 1 includes the identifier of the terminalgroup and address information of the UPF 1.

A session context of the UE 2 includes the identifier of the terminalgroup and address information of the UPF 1.

A session context of the UE 3 includes the identifier of the terminalgroup and address information of the UPF 1.

A session context of the UE 4 includes the identifier of the terminalgroup and address information of the UPF 1.

A session context of the UE 5 includes the identifier of the terminalgroup and address information of the UPF 1.

Storage method 2: A correspondence between the target UPF entity and theidentifier of the terminal group is locally stored.

The first SMF entity locally stores a correspondence between theidentifier of the UPF 1 and the identifier of the terminal group, forexample, in a form of a table or a function mapping relationship. Thisis not limited in this application.

After sending the second instruction information to the first SMFentity, the PCF entity further sends a notification message to a targetnetwork element. The notification message includes the information ofthe terminal group and address information of the first SMF entity, andthe notification message is used to instruct the target network elementto insert the first SMF entity into a session of a third terminal in theterminal group, and instruct the first SMF entity to select a UPF entityused by the third terminal to perform communication.

For example, referring to FIG. 5 , if the target network element is thesecond SMF entity, the SMF 2 in FIG. 5 is the second SMF entity.Certainly, if the terminals in the terminal group further correspond tothe SMF 3 and the SMF 4, the SMF 3 and the SMF 4 are also referred to assecond SMF entities. In other words, the second SMF entities include theSMF 3 and the SMF 4.

The PCF entity sends a notification message to the SMF 2. Thenotification message includes address information of the SMF 1 (thefirst SMF entity) and the information of the terminal group. Optionally,the notification message further includes instruction information. Theinstruction information needs to be sent by the SMF 2 to the SMF 1, andis used to instruct the SMF 1 to select a UPF entity used by a thirdterminal in the terminal group to perform communication. Certainly, thenotification message may alternatively not include the instructioninformation, but implicitly gives an instruction. Details are describedbelow.

The third terminal is a terminal that is in the terminal group and thatis served by the second SMF entity. In FIG. 5 , the third terminal isthe UE 5.

After receiving the foregoing information, the SMF 2 inserts the SMF 1into a session of the UE 5, for example, a PDU session of the UE 5. Inaddition, the SMF 2 further sends a first request message to the SMF 1.The first request message is used to request the SMF 1 to select a UPFentity used by the third terminal, namely, the UE 5, in the terminalgroup to perform communication.

Optionally, if the notification message received by the SMF 2 from thePCF entity includes instruction information, the SMF 2 adds theinstruction information to the first request message, and then sends thefirst request message to the SMF 1. If the notification message does notinclude instruction information, the SMF 2 directly adds the informationof the terminal group to the first request message, and then sends thefirst request message to the SMF 1, to implicitly instruct the SMF 1 toselect a UPF entity used by the third terminal to perform communication.

Herein, the information of the terminal group sent by the SMF 2 to theSMF 1 includes the identifier of the terminal group and an identifier ofthe third terminal in the terminal group, or the information of theterminal group sent by the SMF 2 to the SMF 1 includes the identifier ofthe terminal group and the identifiers of all the terminals in theterminal group.

After receiving the first request message from the SMF 2, the SMF 1obtains, from the contexts of the terminals in the terminal group orfrom the locally stored correspondence between the target UPF entity andthe identifier of the terminal group, the target UPF entity (namely, theUPF 1) selected by the SMF 1 entity for the second terminal (namely, theUE 1 to the UE 4), and then uses the target UPF entity as the target UPFentity of the third terminal (namely, the UE 5).

In other words, the SMF 1 selects the UPF 1 as the target UPF entity ofthe UE 1 to the UE 4 according to the instruction of the PCF entity, andthen receives the first request message sent by the SMF 2. In this case,the SMF 1 directly uses the UPF 1 as the target UPF entity of the UE 5.

Certainly, if the target network element is the AMF entity, animplementation is similar. Details are not described again.

Instruction method 2: The PCF entity directly sends a notificationmessage to a target network element.

In the instruction method, the PCF entity does not send secondinstruction information to the first SMF entity, but directly sends thenotification message to the target network element. The notificationmessage includes the information of the terminal group and addressinformation of the first SMF entity, and the notification message isused to instruct the target network element to insert the first SMFentity into a session of a third terminal in the terminal group, andinstruct the first SMF entity to select a UPF entity used by the thirdterminal to perform communication, or instruct the first SMF entity toselect a UPF entity used by all the terminals in the terminal group toperform communication.

For example, referring to FIG. 5 , an example in which the targetnetwork element is a second SMF entity is used. If the first SMF entityis the SMF 1 and the second SMF entity is the SMF 2, the PCF entitydirectly sends a notification message to the SMF 2. The notificationmessage includes address information of the SMF 1 and the information ofthe terminal group. Optionally, the notification message furtherincludes instruction information. The instruction information is used toinstruct the SMF 1 to select a UPF entity used by the UE 1 to the UE 5to perform group communication. Alternatively, the instructioninformation is used to instruct the SMF 1 to select a UPF entity used bythe UE 5 to perform group communication.

After receiving the notification message from the PCF entity, the SMF 2sends a second request message to the SMF 1. The second request messageis used to request the SMF 1 to select a UPF entity used by the UE 5 inthe terminal group to perform communication, or request the SMF 1 toselect a UPF entity used by the UE 1 to the UE 5 in the terminal groupto perform communication.

Optionally, if the notification message received by the SMF 2 from thePCF entity includes instruction information, the second request messageincludes the instruction information. If the notification messagereceived by the SMF 2 from the PCF entity does not include instructioninformation, the SMF 2 directly adds the information of the terminalgroup to the second request message, and then sends the second requestmessage to the SMF 1, to implicitly instruct the SMF 1 to select a UPFentity used by the UE 1 to the UE 5 to perform communication, orimplicitly instruct the SMF 1 to select a UPF entity used by the UE 5 toperform communication.

Herein, the information of the terminal group sent by the SMF 2 to theSMF 1 includes the identifier of the terminal group and an identifier ofthe third terminal in the terminal group, or the information of theterminal group sent by the SMF 2 to the SMF 1 includes the identifier ofthe terminal group and the identifiers of all the terminals in theterminal group. After receiving the second request message from the SMF2, the SMF 1 selects a target UPF entity for a terminal managed by theSMF 1 and a terminal managed by the SMF 2. For example, the SMF 1selects the UPF 1 as the target UPF entity.

For a specific method for selecting the target UPF entity by the firstSMF entity in the case 3, refer to the specific description of selectingthe target UPF entity in the case 2. Details are not described hereinagain.

Therefore, after the target UPF entity is selected, communicationbetween terminals in the terminal group is locally routed by using theUPF entity, so that a communication path can be shortened. This shortensa transmission path of communication data, and reduces a latency.

In the foregoing three cases, after selecting the target UPF entity usedto perform communication between terminals in the terminal group, thefirst SMF entity further needs to update user plane tunnel informationof some network elements. Descriptions are separately provided below.

For the case 1, the terminals in the terminal group correspond to a sameUPF entity and a same SMF entity. In this case, the first SMF entitydoes not need to update tunnel information.

For the case 2, the terminals in the terminal group correspond todifferent UPF entities but a same SMF entity. In this case, the firstSMF entity may send a first notification message to the target UPFentity. The first notification message includes tunnel information of afirst terminal, and the first terminal indicates a terminal other than aterminal served by the target UPF entity. In other words, a UPF entityaccessed by the first terminal is different from the target UPF entity.For example, referring to FIG. 4 , if the UPF 1 is the target UPFentity, the first terminal is the UE 4 and the UE 5.

The tunnel information of the first terminal includes tunnel informationof a base station accessed by the terminal or tunnel information of aUPF. Specifically, referring to FIG. 4 , tunnel information of a basestation accessed by the UE 4, tunnel information of a base stationaccessed by the UE 5, tunnel information of the UPF 2, and tunnelinformation of the UPF 3 are included.

In addition, the first SMF entity further sends a second notificationmessage to the base station accessed by the first terminal. The secondnotification message includes the tunnel information of the target UPFentity. For example, referring to FIG. 4 , a second notification messageis further sent to the UE 4 and the UE 5, and the second notificationmessage includes tunnel information of the UPF 1.

A path between different network elements may be established by updatingtunnel information, so that the target UPF entity and the base stationaccessed by the first terminal can communicate with each other.

Optionally, a resource of the UPF entity accessed by the first terminalmay be released. For example, resources of the UPF 2 and the UPF 3 arereleased.

For the foregoing case 3, in the instruction method 1, the first requestmessage sent by the target network element to the first SMF entityfurther includes tunnel information of a base station accessed by thethird terminal and/or tunnel information of a UPF entity accessed by thethird terminal.

In the instruction method 2, the second request message sent by thetarget network element to the second SMF entity further includes tunnelinformation of a base station accessed by the third terminal and/ortunnel information of a UPF entity accessed by the third terminal.

For example, referring to FIG. 5 , the first request message or thesecond request message sent by the SMF 2 to the SMF 1 further includestunnel information of a base station accessed by the UE 5 and/or tunnelinformation of the UPF 3. After receiving the tunnel information, theSMF 1 sends the tunnel information of the base station accessed by theUE 5, the tunnel information of the UPF 3, tunnel information of a basestation accessed by the UE 4, and tunnel information of the UPF 2 to theUPF 1 (the target UPF entity), so that the UPF 1 can update tunnelinformation. Further, the SMF 1 further sends tunnel information of theUPF 1 to the UE 4 and the UE 5, so that the UE 4 and the UE 5 can updatetunnel information.

A path between different network elements may be established by updatingthe tunnel information, so that the target UPF entity and the basestation accessed by the first terminal (the UE 4 and the UE 5) cancommunicate with each other.

In this application, the target UPF entity is determined, and the targetUPF entity is used to perform local communication, which is alsoreferred to as closed-loop communication between terminals in theterminal group, so that a communication path between the terminals inthe terminal group can be shortened, and a communication latency can bereduced.

The solutions provided in this application are mainly described abovefrom the perspective of interaction between network elements. It may beunderstood that, to implement the foregoing functions, each networkelement includes a corresponding hardware structure and/or softwaremodule for performing each of the functions. A person of ordinary skillin the art should easily be aware that, in combination with the examplesdescribed in the embodiments disclosed in this specification, units,algorithms steps may be implemented by hardware or a combination ofhardware and computer software. Whether a function is performed byhardware or hardware driven by computer software depends on particularapplications and design constraints of the technical solutions. A personskilled in the art may use different methods to implement the describedfunctions for each particular application, but it should not beconsidered that the implementation goes beyond the scope of the presentinvention.

With reference to the accompanying drawings, the following furtherdescribes the communication method in this application by using specificembodiments.

The following embodiments are described by using an example in which theterminal group is a platoon. The terminals in the terminal group mayalso be referred to as platoon members, and the information of theterminal group may also be referred to as platoon information, whichincludes a platoon identifier and identifiers of the platoon members. Inan application domain, the control function entity may be a V2X controlfunction entity, and the application server may be a V2X applicationserver. The target UPF entity may also be referred to as a serving UPFentity.

Establishment of the platoon may be initiated by UEs in the platoon, ormay be initiated by a V2X control function (V2X-C) entity or a V2Xapplication server (V2X-AS). If establishment of the platoon isinitiated by the UE, the UE generates the platoon information, and sendsthe platoon information to the V2X-C or the V2X-AS. The platooninformation includes at least the platoon identifier and the identifiersof the platoon members (namely, the UEs). If establishment of theplatoon is initiated by the V2X-C or the V2X-AS, the V2X-C or the V2X-ASgenerates the platoon information. Certainly, establishment of theplatoon may be jointly completed by the UE and the V2X-C and/or the UEand the V2X-AS. For example, the UE generates platoon memberinformation, and then the V2X-C and/or the V2X-AS generates anidentifier (ID) of each platoon member. This is not limited in theembodiments of this application.

Embodiment 1

A scenario of Embodiment 1 is as follows: UEs in a platoon member listbelong to a same UPF and a same SMF. FIG. 6 is a schematic diagram of anetwork architecture to which Embodiment 1 is applicable. Two UEs,namely, UE 1 and UE 2, in the platoon member list are used as an examplefor description. In the scenario shown in FIG. 6 , user plane paths ofthe UE 1 and the UE 2 each include a UPF and an A-UPF (anchor UPF).

Currently, according to a prior-art communication method, a flowdirection of data sent by the UE 1 to the UE 2 is: UE 1->base station 1(RAN 1)->UPF->A-UPF->V2XDN->A-UPF->UPF->RAN 2->UE 2.

It can be learned from a current procedure of communication between UEsin the platoon that communication needs to pass through a relativelylarge quantity of network elements, and consequently a relatively greatlatency is caused. To resolve this problem, FIG. 7 shows a communicationmethod according to an embodiment of this application. The communicationmethod includes the following steps.

Step 1: V2X-C or V2X-AS sends platoon information to a PCF, and the PCFreceives the platoon information from the V2X-C or the V2X-AS.

Step 2: The PCF determines that UEs in the platoon information arelocated in a same SMF.

The PCF locally obtains contexts of platoon members based on thereceived platoon information, and obtains, from the contexts of theplatoon members, SMFs in which the UEs are located. In addition, the PCFdetermines that the SMFs in which the UEs are located are a same SMF.

Step 3: The PCF sends instruction information to the SMF, and the SMFreceives the instruction information from the PCF.

The instruction information carries the platoon information, and theinstruction information is used to instruct the SMF to select a servingUPF for the platoon. The SMF is the SMF that is determined in step 2 andin which the UEs are located.

Step 4: The SMF determines that the UEs in the platoon information arelocated in a same UPF.

The SMF locally obtains the contexts of the platoon members based on theplatoon information, and obtains, from the contexts of the platoonmembers, UPFs in which the UEs are located. In addition, the SMFdetermines that the UPFs in which the UEs are located are a same UPF,and the SMF uses the UPF as the serving UPF.

Step 5: The SMF sends local loopback routing information to the UPF, andthe UPF receives the local loopback routing information from the SMF.

The local loopback routing information includes a correspondence betweeneach of the UEs in the platoon member list and a downlink tunnel. Forexample, Table 1 shows an example of representing the local loopbackrouting information in a form of a table.

TABLE 1 Local loopback routing information Identifiers of the platoonmembers Downlink tunnel UE 1 t1 UE 2 t2 . . . . . .

Referring to FIG. 6 , the tunnel t1 is a downlink tunnel between the UPFand the RAN 1, and the tunnel t2 is a downlink tunnel between the UPFand the RAN 2.

After receiving the local loopback routing information, the UPFsubsequently forwards communication data between UEs by using the localloopback routing information. For example, when the UE 1 needs to senddata to the UE 2, according to the communication method in thisembodiment, a communication procedure is: UE 1->RAN 1->UPF->RAN 2->UE 2.The UPF is also referred to as a serving UPF.

Step 6: The UPF sends a response message to the SMF, and the SMFreceives the response message from the UPF.

Step 6 is an optional step, and is performed to notify the SMF that thelocal loopback routing information is received.

Step 7: The SMF sends the platoon information to a UDM.

The UDM may store the received platoon information, so that anothernetwork element can use the platoon information.

Step 7 is an optional step, or step 7 may be performed in any step afterstep 3.

Therefore, according to the method in this embodiment, communicationbetween UEs forms local communication in the serving UPF, so that alatency generated when data is transmitted from the UE 1 to the UE 2 canbe reduced. This facilitates instant communication between platoonmembers.

Embodiment 2

A scenario of Embodiment 2 is as follows: Platoon members (UEs) in aplatoon member list belong to different UPFs but a same SMF. FIG. 8(a)is a schematic diagram of a network architecture to which Embodiment 2is applicable. Two UEs, namely, UE 1 and UE 2, in the platoon memberlist are used as an example for description. In the scenario shown inFIG. 8(a), a user plane path of the UE 1 includes a UPF 1 and an A-UPF 1(anchor UPF), and a user plane path of the UE 2 includes a UPF 2 and anA-UPF 2 (anchor UPF). It may also be understood that the UE 1 belongs tothe UPF 1, the A-UPF 1, and the SMF, and the UE 2 belongs to the UPF 2,the A-UPF 2, and the SMF.

Currently, according to a prior-art communication method, a flowdirection of data sent by the UE 1 to the UE 2 is: UE 1->base station 1(RAN 1)->UPF 1->A-UPF 1->V2XDN->A-UPF 2->UPF 2->base station 2 (RAN2)->UE 2.

It can be learned from the foregoing procedure of communication betweenUEs that communication needs to pass through a relatively large quantityof network elements, and consequently a relatively great latency iscaused. To resolve this problem, FIG. 9 shows a communication methodaccording to an embodiment of this application. The communication methodincludes the following steps.

Step 1: V2X-C or V2X-AS sends platoon information to a PCF, and the PCFreceives the platoon information from the V2X-C or the V2X-AS.

Step 2: The PCF determines that UEs in the platoon information arelocated in a same SMF.

The PCF locally obtains contexts of platoon members based on thereceived platoon information, and obtains, from the contexts of theplatoon members, SMFs in which the UEs are located. In addition, the PCFdetermines that the SMFs in which the UEs are located are a same SMF.

Step 3: The PCF sends instruction information to the SMF, and the SMFreceives the instruction information from the PCF.

The instruction information carries the platoon information, and theinstruction information is used to instruct the SMF to select a servingUPF for the platoon. The SMF is the SMF that is determined in step 2 andin which the UEs are located.

Step 4: The SMF determines to use the UPF 1 as the serving UPF.

The SMF locally obtains the contexts of the platoon members based on theplatoon information, and obtains, from the contexts of the platoonmembers, UPFs in which the UEs are located. Further, the SMF determinesthat the UE 1 belongs to the UPF 1 and the A-UPF 1, and determines thatthe UE 2 belongs to the UPF 2 and the A-UPF 2. In this case, the SMFselects a UPF from the UPF 1 and the UPF 2 to serve as the serving UPF.

For example, the serving UPF may be selected according to one or more ofthe following methods:

(1) A UPF with a lower load is selected as the serving UPF based onloads of UPFs on user plane paths of the UE 1 and the UE 2, namely,loads of the UPF 1 and the UPF 2.

(2) A UPF that serves a larger quantity of UEs in the platoon isselected as the serving UPF.

(3) A UPF closer to UE in the platoon is selected as the serving UPF.

Optionally, a new UPF may be selected as the serving UPF. The new UPF isa UPF other than the UEs in the platoon.

Herein, an example in which the UPF 1 is selected as the serving UPF isused for description.

Step 5: The SMF sends a user plane establishment message to the UPF 1,and the UPF 1 receives the user plane establishment message from theSMF.

The user plane establishment message includes user plane information ofthe UE 2, local loopback routing information, and tunnel information ofthe A-UPF 2. The user plane information of the UE 2 includes informationabout a tunnel from the UPF 1 to the RAN 2.

After the UPF 1 receives the user plane establishment message, the UPF 1may obtain a path from the UPF 1 to the RAN 2 and a path from the UPF 1to the A-UPF 2.

For content and a function of the local loopback routing information,refer to Table 1 in Embodiment 1. Details are not described hereinagain.

Step 6: The UPF 1 sends a response message to the SMF, and the SMFreceives the response message from the UPF 1.

Step 6 is an optional step, and is performed to notify the SMF that anotification message is received.

Step 7: The SMF sends a UPF reselection notification message to the basestation 2 (RAN 2), and the base station 2 (RAN 2) receives the UPFreselection notification message from the SMF.

The UPF reselection notification message includes tunnel information ofa downlink user plane of the UPF 1 (which is a user plane of the UE 2).Therefore, the base station 2 (RAN 2) may obtain a path of the UPF 1, inother words, establish a user plane path from the base station 2 (RAN 2)to the UPF 1.

Step 8: The base station 2 (RAN 2) sends a response message to the SMF,and the SMF receives the response message from the base station 2 (RAN2).

Step 8 is an optional step, and is performed to notify the SMF that theUPF reselection notification message is received.

Step 9: The SMF sends a user plane update message to the A-UPF 2, andthe A-UPF 2 receives the user plane update message from the SMF.

The user plane update message is used to update user plane tunnelinformation, and the user plane update message carries tunnelinformation of an uplink user plane of the UPF 1. Therefore, a userplane path from the A-UPF 2 to the UPF 1 is established.

Step 10: The A-UPF 2 sends a response message to the SMF, and the SMFreceives the response message from the A-UPF 2.

Step 10 is an optional step, and is performed to notify the SMF that theuser plane update message is received.

Step 11: The SMF sends a UE user plane release message to the UPF 2, andthe UPF 2 receives the UE user plane release message from the SMF.

After receiving the UE user plane release message, the UPF 2 releasesinformation about a user plane tunnel between the UPF 2 and the RAN 2.

Step 12: The SMF sends the platoon information to a UDM.

The UDM may store the received platoon information, so that anothernetwork element can use the platoon information.

Step 12 is an optional step, or step 12 may be performed in any stepafter step 3.

According to the method in this embodiment, a network side may redirectthe UEs in the platoon to a same UPF. The UPF is used as the serving UPFof the platoon, and communication between UEs in the platoon is locallyimplemented in the serving UPF. In this embodiment, the SMF determinesto use the UPF 1 as the serving UPF of the platoon, to reselect a UPFfor the UE 2, for example, the UPF 1 instead of the UPF 2. Therefore,after the UPF 1 is reselected for the UE 2, the system architectureshown in FIG. 8(a) is updated with the system architecture shown in FIG.8(b). To be specific, the path between the RAN 2 and the UPF 1 and thepath between the UPF 1 and the A-UPF 2 are established, and the pathbetween the UPF 2 and the RAN 2 is released. Therefore, when the UE 1needs to send data to the UE 2, according to the communication method inthis embodiment, the communication procedure is: UE 1->RAN 1->UPF 1->RAN2->UE 2. The UPF 1 is also referred to as the serving UPF. According tothe method in this embodiment, a latency generated when the data istransmitted from the UE 1 to the UE 2 can be reduced. This facilitatesinstant communication between platoon members.

Embodiment 3

A scenario of Embodiment 3 is as follows: UEs in a platoon member listbelong to different UPFs but a same SMF. FIG. 10(a) is a schematicdiagram of a network architecture to which Embodiment 3 is applicable. Amain difference between this application scenario and the applicationscenario shown in FIG. 10(a) lies in as follows: In FIG. 10(a), there isonly one UPF on a user plane of UE 2, namely, an anchor UPF, which isreferred to as an A-UPF 2. When an SMF selects a UPF 1 as a serving UPF,a user plane tunnel of the anchor UPF cannot be released, in otherwords, the UPF 1 cannot be reselected for UE 2 and user plane tunnelinformation of the A-UPF 2 cannot be released according to the method inEmbodiment 2. Therefore, in the scenario of Embodiment 3, a method forinserting the serving UPF may be used to complete UPF redirection.

As shown in FIG. 10(b), the UPF 1 is inserted between a RAN 2 and theA-UPF 2, and tunnel information of the UPF 1, tunnel information of theRAN 2, and tunnel information of the A-UPF 2 are separately updated, sothat a latency of data transmission between UE 1 and the UE 2 can alsobe reduced. For example, when the UE 1 needs to send data to the UE 2,according to the communication method in this embodiment, acommunication procedure is: UE 1->RAN 1->UPF 1->RAN 2->UE 2. The UPF 1is also referred to as the serving UPF. According to the method in thisembodiment, a latency generated when the data is transmitted from the UE1 to the UE 2 can be reduced. This facilitates instant communicationbetween platoon members.

Embodiment 4

A scenario of Embodiment 4 is as follows: UEs in a platoon member listbelong to different UPFs and different SMFs. FIG. 11(a) is a schematicdiagram of a network architecture to which Embodiment 4 is applicable.Two UEs, namely, UE 1 and UE 2, in the platoon member list are used asan example for description. In the scenario shown in FIG. 11(a), a userplane path of the UE 1 includes a UPF 1 and an A-UPF 1 (anchor UPF), anda user plane path of the UE 2 includes a UPF 2 and an A-UPF 2 (anchorUPF). It may also be understood that the UE 1 belongs to the UPF 1, theA-UPF 1, and an SMF 1, and the UE 2 belongs to the UPF 2, the A-UPF 2,and an SMF 2.

It should be noted that, in the scenario of this embodiment, a userplane path of each UE may include only one anchor UPF, or may includeone anchor UPF and a plurality of other UPFs. For example, referring toFIG. 11(a), the UE 1 is used as an example. The user plane path of theUE 1 includes only the A-UPF 1, in other words, the UPF 1 in the figureis deleted, or may include the A-UPF 1 and a plurality of other UPFs(only one UPF, namely, the UPF 1, is shown in the figure). In thisembodiment, the user plane path of each UE needs to include at least oneUPF.

The following uses the scenario shown in FIG. 11(a) as an example fordescription. Currently, according to a prior-art communication method, aflow direction of data sent by the UE 1 to the UE 2 is: UE 1->basestation 1 (RAN 1)->UPF 1->A-UPF 1->DN->A-UPF 2->UPF 2->base station 2(RAN 2)->UE 2.

It can be learned from the foregoing procedure of communication betweenUEs that communication needs to pass through a relatively large quantityof network elements, and consequently a relatively great latency iscaused. To resolve this problem, FIG. 12 shows a communication methodaccording to an embodiment of this application. The communication methodincludes the following steps.

Step 1: V2X-C or V2X-AS sends platoon information to a PCF, and the PCFreceives the platoon information from the V2X-C or the V2X-AS.

Step 2: The PCF determines that the SMF 1 is a serving UPF.

In this step, after receiving the platoon information, the PCF locallyobtains contexts of platoon members based on the platoon information,and may obtain, based on the contexts, SMFs in which UEs are located,and determine that the UEs in the platoon belong to different SMFs.Specifically, the UEs belong to at least two SMFs. For example, theplatoon members are the UE 1, the UE 2, UE 3, UE 4, and UE 5. The UE 1,the UE 2, and the UE 3 belong to the SMF 1, and the UE 4 and the UE 5belong to the SMF 2. For another example, the UE 1, the UE 2, and the UE3 belong to the SMF 1, the UE 4 belongs to the SMF 2, and the UE 5belongs to an SMF 3. In this embodiment, two UEs, namely, the UE 1 andthe UE 2, are used as an example. For example, the UE 1 belongs to theSMF 1, and the UE 2 belongs to the SMF 2.

Further, the PCF selects an SMF as a serving SMF. For example, a methodfor selecting the serving SMF may be selecting an SMF that covers alargest quantity of UEs in the platoon to serve as the serving SMF.

Optionally, a new SMF may be selected as the serving SMF. The new SMF isan SMF other than the UEs in the platoon.

In this embodiment, an example in which the PCF selects the SMF 1 as theserving SMF is used for description.

Step 3: The PCF sends a notification message to the SMF 2, and the SMF 2receives the notification message from the PCF, where the notificationmessage is used to instruct the SMF 2 to insert the SMF 1 into a PDUsession of the UE 2, in other words, the SMF 1 is also used as an SMF towhich the UE 2 belongs.

The notification message includes the following information:

(1) Address of the SMF 1 and first instruction information, where thefirst instruction information is used to instruct the SMF 2 to insertthe SMF 1 into the PDU session of the UE 2, in other words, the SMF 1 isalso used as the SMF to which the UE 2 belongs.

(2) Platoon information, where the platoon information needs to beforwarded by the SMF 2 to the SMF 1.

Optionally, the notification message further includes the followinginformation:

(3) Second instruction information, where the second instructioninformation needs to be forwarded by the SMF 2 to the SMF 1, and is usedto instruct the SMF 1 to select the serving UPF for the UEs in theplatoon. Certainly, the notification message may not include the secondinstruction information. In other words, the SMF 1 may be implicitlyinstructed to select the serving UPF for the UEs in the platoon.

Step 4: The SMF 2 sends a session establishment request message to theSMF 1, and the SMF 1 receives the session establishment request messagefrom the SMF 2.

The session establishment request message includes the followinginformation:

(1) User plane downlink tunnel of the UPF 2.

(2) Uplink tunnel information of the RAN 2.

(3) Platoon information.

Optionally, the session establishment request message further includesthe following information:

(4) Second instruction information.

The information (3) and the information (4) are from the PCF entity.

After receiving the session establishment request message, the SMF 1selects the serving UPF. For a selection method, refer to the method forselecting a UPF in Embodiment 2. Details are not described herein again.

In this embodiment, an example in which the UPF 1 is selected as theserving UPF is used for description.

It should be noted that, in step 3 and step 4, the PCF entity firstsends the notification message to the SMF 2, and then the SMF 2 sendsthe session establishment request message to the SMF 1. Optionally, step3 and step 4 may be replaced with step A to step C.

Step A: The PCF sends a notification message to the SMF 1, and the SMF 1receives the notification message from the PCF.

The notification message includes the platoon information, and theplatoon information includes a platoon identifier and identifiers of theplatoon members. Optionally, the identifiers of all the platoon membersmay be included, or only an identifier of a platoon member managed bythe SMF 1 may be included.

Optionally, the notification message further includes instructioninformation, and the instruction information is used to instruct the SMF1 to select the serving UPF.

If the notification message does not include the instructioninformation, the notification message is used to implicitly instruct, byusing the sent platoon information, the SMF 1 to select the serving UPF.

After receiving the notification message, the SMF 1 selects the servingUPF, for example, selects the UPF 1 as the serving UPF. In addition, theSMF 1 further stores the serving UPF. For a storage manner, refer to thespecific description in the foregoing embodiment. Details are notdescribed herein again.

Step B: The PCF sends a notification message to the SMF 2, and the SMF 2receives the notification message from the PCF.

The notification message is used to instruct the SMF 2 to insert the SMF1 into a PDU session of the UE 2. In other words, the SMF 1 is also usedas an SMF to which the UE 2 belongs.

Content included in the notification message is the same as the contentthat is carried in the notification message and that is described instep 3. Details are not described herein again. For details, refer tothe foregoing description.

Step C: The SMF 2 sends a session establishment request message to theSMF 1, and the SMF 1 receives the session establishment request messagefrom the SMF 2.

For content included in the session establishment request message, referto the content that is carried in the session establishment requestmessage and that is described in step 4. However, it should be notedthat the platoon information carried in the session establishmentrequest message may include only a platoon member in the platoon that ismanaged by the SMF 2, or may include all the members in the platoon.

After receiving the session establishment request message, the SMF 1selects a serving UPF for a terminal managed by the SMF 2. In step A,the SMF 1 has selected and stored the serving UPF for the terminalmanaged by the SMF 1. Therefore, the serving UPF that has been selectedby the SMF 1 may be directly used as the serving UPF of the terminalmanaged by the SMF 2. In other words, the selected UPF 1 is used as theserving UPF of the terminal managed by the SMF 2.

Step 5: The SMF 1 sends a user plane establishment message to the UPF 1,and the UPF 1 receives the user plane establishment message from the SMF1.

The user plane establishment message includes tunnel information of theUPF 2, uplink tunnel information of the RAN 2, and local loopbackrouting information.

After the UPF 1 receives the user plane establishment message, the UPF 1may establish a path from the UPF 1 to the UPF 2 and a path from the UPF1 to the RAN 2.

For content and a function of the local loopback routing information,refer to Table 1 in Embodiment 1. Details are not described hereinagain.

Step 6: The UPF 1 sends a response message to the SMF 1, and the SMF 1receives the response message from the UPF 1.

Step 6 is an optional step, and is performed to notify the SMF 1 that anotification message is received.

Step 7: The SMF 1 sends a response message to the SMF 2, and the SMF 2receives the response message from the SMF 1.

The response message includes a downlink tunnel of the UPF 1.

Step 8: The SMF 2 sends a user plane update message to the UPF 2, andthe UPF 2 receives the user plane update message from the SMF 2.

The user plane update message includes tunnel information of the UPF 1.

Therefore, the UPF 2 may establish a path from the UPF 2 to the UPF 1.

Step 9: The UPF 2 sends a response message to the SMF 2, and the SMF 2receives the response message from the UPF 2.

Step 9 is an optional step, and is performed to notify the SMF 2 thatthe user plane update message is received.

Step 10: The SMF 2 sends a user plane tunnel update message to the basestation 2 (RAN 2), and the base station 2 (RAN 2) receives the userplane tunnel update message from the SMF 2.

The user plane tunnel update message includes the downlink tunnel of theUPF 1, and the downlink tunnel of the UPF 1 is obtained by the SMF 2 instep 7.

Therefore, the base station 2 (RAN 2) may update a user plane path, andestablish a path from the base station 2 (RAN 2) to the UPF 1.

Step 11: The SMF 1 sends the platoon information to a UDM.

The UDM may store the received platoon information, so that anothernetwork element can use the platoon information.

Step 11 is an optional step, or step 11 may be performed in any stepafter step 4.

According to the method in this embodiment, a network side may redirectthe UEs in the platoon to a same SMF, and the SMF is used as the servingSMF of the platoon. In addition, the network side may redirect the UEsin the platoon to a same UPF, and the UPF is used as the serving UPF ofthe platoon. Communication between UEs in the platoon is locallyimplemented in the serving UPF. In this embodiment, the serving SMF(namely, the SMF 1) determines to use the UPF 1 as the serving UPF ofthe platoon, to insert a UPF for the UE 2, and insert the UPF 1 betweenthe RAN 2 and the UPF 2. After the UPF 1 is inserted between the RAN 2and the UPF 2, the system architecture shown in FIG. 11(a) is updatedwith the system architecture shown in FIG. 11(b). To be specific, thepath between the RAN 2 and the UPF 1, the path between the UPF 1 and theUPF 2, and the path between the UPF 2 and the SMF 1 are established.Therefore, when the UE 1 needs to send data to the UE 2, according tothe communication method in this embodiment, the communication procedureis: UE 1->RAN 1->UPF 1->RAN 2->UE 2. The UPF 1 is also referred to asthe serving UPF. According to the method in this embodiment, a latencygenerated when the data is transmitted from the UE 1 to the UE 2 can bereduced. This facilitates instant communication between platoon members.

It should be noted that all the procedures performed by the SMF 2 inEmbodiment 4 may be implemented by the AMF entity. For a process inwhich the AMF entity implements the foregoing embodiment, refer to theimplementation process of the SMF 2. Details are not described again.Based on a same inventive concept, FIG. 13 is a schematic diagram of anapparatus according to an embodiment of this application. The apparatusmay be a session management function entity, and may perform the methodperformed by the first session management function entity (the first SMFentity) in any one of the foregoing embodiments. Alternatively, theapparatus may be a policy control function entity, and may perform themethod performed by the policy control function entity (the PCF entity)in any one of the foregoing embodiments.

The apparatus 1300 includes at least one processor 131 and a transceiver132. Optionally, the apparatus 1300 further includes a memory 133. Theprocessor 131, the transceiver 132, and the memory 133 are connected byusing a communications line.

The processor 131 may be a general-purpose central processing unit(CPU), a microprocessor, an application-specific integrated circuit(ASIC), or one or more integrated circuits configured to control programexecution of the solutions of the present invention.

The communications line may include a path for transmitting informationbetween the foregoing units.

The transceiver 132 is configured to communicate with another device ora communications network, and the transceiver includes a radio frequencycircuit.

The memory 133 may be a read-only memory (ROM) or another type of staticstorage device capable of storing static information and instructions,or a random access memory (RAM) or another type of dynamic storagedevice capable of storing information and instructions. Alternatively,the memory 133 may be an electrically erasable programmable read-onlymemory (EEPROM), a compact disc read-only memory (CD-ROM) or anotheroptical disk storage, an optical disc storage (including a compactoptical disc, a laser disc, an optical disc, a digital versatile disc, aBlu-ray disc, or the like), a magnetic disk storage medium or anothermagnetic storage device, or any other medium that can be configured tocarry or store expected program code in a form of an instruction or adata structure and that can be accessed by a computer. However, this isnot limited herein. The memory 133 may exist independently, and isconnected to the processor 131 by the communications line.Alternatively, the memory 133 may be integrated into the processor. Thememory 133 is configured to store application program code for executingthe solutions of the present invention, and the processor 131 controlsthe execution. The processor 131 is configured to execute theapplication program code stored in the memory 133.

In a specific implementation, in an embodiment, the processor 131 mayinclude one or more CPUs, for example, a CPU 0 and a CPU 1 in FIG. 13 .

In specific implementation, in an embodiment, the apparatus 1300 mayinclude a plurality of processors, for example, the processor 131 and aprocessor 138 in FIG. 13 . Each of the processors may be a single-coreprocessor (single-CPU), or may be a multi-core processor (multi-CPU).The processor herein may be one or more devices, circuits, and/orprocessing cores for processing data (for example, a computer programinstruction).

It should be understood that, when the apparatus is a session managementfunction entity, the apparatus may be configured to implement the stepsperformed by the first session management function entity (the first SMFentity) in the communication method in the embodiments of the presentinvention. For a related feature, refer to the foregoing description.Details are not described herein again.

It should be understood that, when the apparatus is a policy controlfunction entity, the apparatus may be configured to implement the stepsperformed by the policy control function entity (the PCF entity) in thecommunication method in the embodiments of the present invention. For arelated feature, refer to the foregoing description. Details are notdescribed herein again.

In this application, the session management function entity may bedivided into function modules based on the foregoing method examples.For example, function modules corresponding to various functions may beobtained through division, or two or more functions may be integratedinto one processing module. The integrated module may be implemented ina form of hardware, or may be implemented in a form of a softwarefunction module. It should be noted that, in this application, moduledivision is an example, and is merely a logical function division. Inactual implementation, another division manner may be used. For example,when each function module is obtained through division based on eachcorresponding function, FIG. 14 is a schematic diagram of an apparatus.The apparatus may be the first session management function entity (thefirst SMF entity) in the foregoing embodiment. The apparatus includes aprocessing unit 1401 and a communications unit 1402.

In this embodiment, the session management function entity is presentedin a form in which each function module is obtained through divisionbased on each corresponding function, or the session management functionentity is presented in a form in which each function module is obtainedthrough division in an integrated manner. The “module” herein may be anapplication-specific integrated circuit (ASIC), a circuit, a processorand a memory for executing one or more software or firmware programs, anintegrated logic circuit, and/or another device that can provide theforegoing function.

It should be understood that the session management function entity maybe configured to implement the steps performed by the first sessionmanagement function entity (the first SMF entity) in the communicationmethod in the embodiments of the present invention. For a relatedfeature, refer to the foregoing description. Details are not describedherein again.

In this application, the policy control function entity may be dividedinto function modules based on the foregoing method examples. Forexample, function modules corresponding to various functions may beobtained through division, or two or more functions may be integratedinto one processing module. The integrated module may be implemented ina form of hardware, or may be implemented in a form of a softwarefunction module. It should be noted that, in this application, moduledivision is an example, and is merely a logical function division. Inactual implementation, another division manner may be used. For example,when each function module is obtained through division based on eachcorresponding function, FIG. 15 is a schematic diagram of an apparatus.The apparatus may be the policy control function entity in the foregoingembodiment. The apparatus includes a processing unit 1501 and acommunications unit 1502.

In this embodiment, the policy control function entity is presented in aform in which each function module is obtained through division based oneach corresponding function, or the policy control function entity ispresented in a form in which each function module is obtained throughdivision in an integrated manner. The “module” herein may be anapplication-specific integrated circuit (ASIC), a circuit, a processorand a memory for executing one or more software or firmware programs, anintegrated logic circuit, and/or another device that can provide theforegoing function.

It should be understood that the policy control function entity may beconfigured to implement the steps performed by the policy controlfunction entity (the PCF entity) in the communication method in theembodiments of the present invention. For a related feature, refer tothe foregoing description. Details are not described herein again.

All or some of the foregoing embodiments may be implemented by usingsoftware, hardware, firmware, or any combination thereof. When softwareis used to implement the embodiments, all or some of the embodiments maybe implemented in a form of a computer program product. The computerprogram product includes one or more computer instructions. When thecomputer program instructions are loaded or executed on a computer, allor some of the procedures or functions according to the embodiments ofthe present invention are generated. The computer may be ageneral-purpose computer, a dedicated computer, a computer network, oranother programmable apparatus. The computer instructions may be storedin a computer-readable storage medium or may be transmitted from acomputer-readable storage medium to another computer-readable storagemedium. For example, the computer instructions may be transmitted from awebsite, computer, server, or data center to another website, computer,server, or data center in a wired (for example, a coaxial cable, anoptical fiber, or a digital subscriber line (DSL)) or wireless (forexample, infrared, radio, or microwave) manner. The computer-readablestorage medium may be any usable medium accessible by the computer, or adata storage device, such as a server or a data center, integrating oneor more usable media. The usable medium may be a magnetic medium (forexample, a floppy disk, a hard disk, or a magnetic tape), an opticalmedium (for example, a DVD), a semiconductor medium (for example, asolid state disk (SSD), or the like.

Although the present invention is described with reference to theembodiments, in a process of implementing the present invention thatclaims protection, a person skilled in the art may understand andimplement another variation of the disclosed embodiments by viewing theaccompanying drawings, disclosed content, and the accompanying claims.In the claims, “comprising” does not exclude another component oranother step, and “a” or “one” does not exclude a meaning of plurality.A single processor or another unit may implement several functionsenumerated in the claims. Some measures are recorded in dependent claimsthat are different from each other, but this does not mean that thesemeasures cannot be combined to produce a better effect.

A person skilled in the art should understand that the embodiments ofthis application may be provided as a method, an apparatus (device), acomputer readable storage medium, or a computer program product.Therefore, this application may use a form of hardware only embodiments,software only embodiments, or embodiments with a combination of softwareand hardware. They are collectively referred to as “modules” or“systems”.

A person skilled in the art may further understand that variousillustrative logical blocks and steps that are listed in the embodimentsof this application may be implemented by using electronic hardware,computer software, or a combination thereof. Whether the functions areimplemented by using hardware or software depends on particularapplications and a design requirement of the entire system. A person ofordinary skill in the art may use various methods to implement thedescribed functions for each particular application, but it should notbe considered that the implementation goes beyond the scope of theembodiments of this application.

The various illustrative logical units and circuits described in theembodiments of the present invention may implement or operate thedescribed functions by using a general processor, a digital signalprocessor, an application-specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or another programmable logicalapparatus, a discrete gate or transistor logic, a discrete hardwarecomponent, or a design of any combination thereof. The general processormay be a microprocessor. Optionally, the general processor may also beany conventional processor, controller, microcontroller, or statemachine. The processor may also be implemented by a combination ofcomputing apparatuses, such as a digital signal processor and amicroprocessor, multiple microprocessors, one or more microprocessorswith a digital signal processor core, or any other similarconfiguration.

Steps of the methods or algorithms described in the embodiments of thisapplication may be directly embedded into hardware, a software unitexecuted by a processor, or a combination thereof. The software unit maybe stored in a RAM memory, a flash memory, a ROM memory, an EPROMmemory, an EEPROM memory, a register, a hard disk, a removable magneticdisk, a CD-ROM, or a storage medium of any other form in the art. Forexample, the storage medium may connect to a processor so that theprocessor may read information from the storage medium and writeinformation to the storage medium. Alternatively, the storage medium mayfurther be integrated into a processor. The processor and the storagemedium may be arranged in an ASIC, and the ASIC may be arranged interminal device. Alternatively, the processor and the storage medium mayalso be arranged in different components of the terminal device.

In one or more example designs, the functions described in theembodiments of this application may be implemented by using hardware,software, firmware, or any combination thereof. If the present inventionis implemented by software, these functions may be stored in acomputer-readable medium or are transmitted to the computer-readablemedium in a form of one or more instructions or code. Thecomputer-readable medium is either a computer storage medium or acommunications medium that enables a computer program to move from oneplace to another. The storage medium may be an available medium that maybe accessed by any general or special computer. For example, such acomputer-readable medium may include but is not limited to a RAM, a ROM,an EEPROM, a CD-ROM, or another optical disc storage, a disk storage oranother magnetic storage apparatus, or any other medium that may be usedto carry or store program code, where the program code is in a form ofan instruction or a data structure or in a form that can be read by ageneral or special computer or a general or special processor. Inaddition, any connection may be appropriately defined as acomputer-readable medium. For example, if software is transmitted from awebsite, a server, or another remote resource by using a coaxial cable,an optical fiber computer, a twisted pair, a digital subscriber line(DSL) or in a wireless manner, such as infrared, radio, or microwave,the software is included in a defined computer-readable medium. The disc(disk) and the disk (disc) and the disk (disk) include a compresseddisk, a laser disk, an optical disc, a DVD, a floppy disk, and a Blu-raydisc. The disk generally copies data by a magnetic means, and the discgenerally copies data optically by a laser means. The foregoingcombination may also be included in the computer-readable medium.

This application is described with reference to the flowcharts and/orblock diagrams of the method, the apparatus (device), and the computerprogram product according to an embodiment of this application. Itshould be understood that computer program instructions may be used toimplement each process and/or each block in the flowcharts and/or theblock diagrams and a combination of a process and/or a block in theflowcharts and/or the block diagrams. These computer programinstructions may be provided for a general-purpose computer, a dedicatedcomputer, an embedded processor, or a processor of any otherprogrammable data processing device to generate a machine, so that theinstructions executed by a computer or a processor of any otherprogrammable data processing device generate an apparatus forimplementing a specific function in one or more processes in theflowcharts and/or in one or more blocks in the block diagrams.

Although the present invention is described with reference to specificfeatures and the embodiments thereof, obviously, various modificationsand combinations may be made to them without departing from the spiritand scope of the present invention. Correspondingly, the specificationand accompanying drawings are merely example description of the presentinvention defined by the accompanying claims, and is considered as anyof or all modifications, variations, combinations or equivalents thatcover the scope of the present invention. Obviously, a person skilled inthe art can make various modifications and variations to the presentinvention without departing from the spirit and scope of the presentinvention. The present invention is intended to cover thesemodifications and variations provided that they fall within the scope ofprotection defined by the following claims and their equivalenttechnologies.

What is claimed is:
 1. A communication method, comprising: determining,by a session management function entity based on information of aterminal group, one or more user plane function entities accessed by oneor more terminals in the terminal group; selecting, by the sessionmanagement function entity, a target user plane function entity from theone or more user plane function entities accessed by the one or moreterminals; and sending, by the session management function entity,routing information to the target user plane function entity, whereinthe routing information is configured for communication betweenterminals in the terminal group through the target user plane functionentity, and the communication does not pass through a data network. 2.The method according to claim 1, wherein selecting, by the sessionmanagement function entity, the target user plane function entity fromthe one or more user plane function entities accessed by the one or moreterminals comprises: selecting, by the session management functionentity, the target user plane function entity from the one or more userplane function entities accessed by the one or more terminals based onone or more of following: a service range of the one or more user planefunction entities accessed by the one or more terminals, locations ofthe terminals in the terminal group, or a quantity of terminals in theterminal group that are served by the one or more user plane functionentities accessed by the one or more terminals.
 3. The method accordingto claim 1, wherein the method further comprises: sending, by thesession management function entity, a first notification message to thetarget user plane function entity, wherein the first notificationmessage comprises tunnel information of a first terminal in the terminalgroup, and a user plane function entity accessed by the first terminalis different from the target user plane function entity.
 4. The methodaccording to claim 3, wherein the method further comprises: sending, bythe session management function entity, a second notification message toa base station accessed by the first terminal, wherein the secondnotification message comprises tunnel information of the target userplane function entity; and receiving, by the base station, the secondnotification message.
 5. The method according to claim 1, wherein themethod further comprises: receiving, by the session management functionentity from a policy control function entity, first instructioninformation, wherein the first instruction information instructs thesession management function entity to select a user plane functionentity used by a terminal in the terminal group to performcommunication.
 6. The method according to claim 1, wherein the methodfurther comprises: receiving, by the session management function entityfrom a policy control function entity, second instruction information,wherein the second instruction information instructs the sessionmanagement function entity to select a user plane function entityaccessed by a second terminal in the terminal group to performcommunication, and the second terminal corresponds to the sessionmanagement function entity; and wherein determining, by the sessionmanagement function entity, the target user plane function entity basedon the one or more user plane function entities accessed by the one ormore terminals comprises: determining, by the session managementfunction entity, the target user plane function entity based on the userplane function entity accessed by the second terminal.
 7. The methodaccording to claim 1, wherein the method further comprises: receiving,by the session management function entity, a second request message froma target network element, wherein the second request message requeststhe session management function entity to select a user plane functionentity accessed by a third terminal in the terminal group to performcommunication, and the third terminal corresponds to the target networkelement; and wherein determining, by the session management functionentity, the target user plane function entity based on the one or moreuser plane function entities accessed by the one or more terminalscomprises: determining, by the session management function entity, thetarget user plane function entity based on a user plane function entityaccessed by a second terminal in the terminal group, wherein the secondterminal corresponds to the session management function entity, and thetarget network element is a second session management function entity oran access and mobility management function entity.
 8. The methodaccording to claim 1, wherein information of the terminal groupcomprises an identifier of the terminal group and identifiers of theterminals in the terminal group; and the method further comprises:storing, by the session management function entity, the target userplane function entity and the identifier of the terminal group incontexts of the terminals in the terminal group, wherein the sessionmanagement function entity is configured to, according to the context ofthe terminals in the terminal group, obtain the target user planefunction entity from the contexts of the terminals in the terminalgroup; or locally storing, by the session management function entity, acorrespondence between the target user plane function entity and theidentifier of the terminal group, wherein the session managementfunction entity is configured to obtain the target user plane functionentity from the correspondence.
 9. The method according to claim 1,wherein selecting, by the session management function entity, the targetuser plane function entity from the one or more user plane functionentities accessed by the one or more terminals comprises: selecting, bythe session management function entity, the target user plane functionentity from the one or more user plane function entities accessed by theone or more terminals based on a load of the one or more user planefunction entities accessed by the one or more terminals.
 10. Anapparatus, comprising: at least one processor, and a non-transitorymemory storing computer-executable instructions; wherein thecomputer-executable instructions, when executed by the at least oneprocessor, cause the apparatus to: determine, based on information of aterminal group, one or more user plane function entities accessed by oneor more terminals in the terminal group; select a target user planefunction entity from the one or more user plane function entitiesaccessed by the one or more terminals; and send routing information tothe target user plane function entity, wherein the routing informationis configured for communication between terminals in the terminal groupthrough the target user plane function entity, and the communicationdoes not pass through a data network.
 11. The apparatus according toclaim 10, wherein the computer-executable instructions, when executed bythe at least one processor, cause the apparatus further to: select thetarget user plane function entity from the one or more user planefunction entities accessed by the one or more terminals based on one ormore of following: a service range of the one or more user planefunction entities accessed by the one or more terminals, locations ofthe terminals in the terminal group, or a quantity of terminals in theterminal group that are served by the one or more user plane functionentities accessed by the one or more terminals.
 12. The apparatusaccording to claim 10, wherein the computer-executable instructions,when executed by the at least one processor, cause the apparatus furtherto: send a first notification message to the target user plane functionentity, wherein the first notification message comprises tunnelinformation of a first terminal in the terminal group, and a user planefunction entity accessed by the first terminal is different from thetarget user plane function entity.
 13. The apparatus according to claim12, wherein the computer-executable instructions, when executed by theat least one processor, cause the apparatus further to: send a secondnotification message to a base station accessed by the first terminal,wherein the second notification message comprises tunnel information ofthe target user plane function entity.
 14. The apparatus according toclaim 10, wherein the computer-executable instructions, when executed bythe at least one processor, cause the apparatus further to: receivefirst instruction information, wherein the first instruction informationinstructs the apparatus to select a user plane function entity used by aterminal in the terminal group to perform communication.
 15. Theapparatus according to claim 10, wherein the computer-executableinstructions, when executed by the at least one processor, cause theapparatus further to: send second instruction information, wherein thesecond instruction information instructs the apparatus to select a userplane function entity accessed by a second terminal in the terminalgroup to perform communication, and the second terminal corresponds tothe apparatus; and determine the target user plane function entity basedon the user plane function entity accessed by the second terminal. 16.The apparatus according to claim 10, wherein information of the terminalgroup comprises an identifier of the terminal group and identifiers ofthe terminals in the terminal group; and the computer-executableinstructions, when executed by the at least one processor, cause theapparatus further to: store the target user plane function entity andthe identifier of the terminal group in contexts of the terminals in theterminal group, wherein the apparatus is configured to obtain the targetuser plane function entity from the contexts of the terminals in theterminal group; or locally store a correspondence between the targetuser plane function entity and the identifier of the terminal group,wherein the apparatus is configured to obtain the target user planefunction entity from the correspondence.
 17. The apparatus according toclaim 10, wherein the computer-executable instructions, when executed bythe at least one processor, cause the apparatus further to: select thetarget user plane function entity from the one or more user planefunction entities accessed by the one or more terminals based on a loadof the one or more user plane function entities accessed by the one ormore terminals.
 18. A non-transitory storage medium, comprisingcomputer-executable instructions which, when executed by at least oneprocessor of an apparatus, cause the apparatus to: determine, based oninformation of a terminal group, one or more user plane functionentities accessed by one or more terminals in the terminal group; selecta target user plane function entity from the one or more user planefunction entities accessed by the one or more terminals; and sendrouting information to the target user plane function entity, whereinthe routing information is configured for communication betweenterminals in the terminal group through the target user plane functionentity, and the communication does not pass through a data network. 19.The non-transitory storage medium according to claim 18, wherein thecomputer-executable instructions, when executed by the at least oneprocessor, cause the apparatus further to: select the target user planefunction entity from the one or more user plane function entitiesaccessed by the one or more terminals based on one or more of following:a service range of the one or more user plane function entities accessedby the one or more terminals, locations of the terminals in the terminalgroup, or a quantity of terminals in the terminal group that are servedby the one or more user plane function entities accessed by the one ormore terminals.
 20. The non-transitory storage medium according to claim18, wherein the computer-executable instructions, when executed by theat least one processor, cause the apparatus further to: receive a firstinstruction information, wherein the first instruction informationinstructs the apparatus to select a user plane function entity used by aterminal in the terminal group to perform communication.